The role of communication satellites is essentially to retransmit after amplification signals transmitted by transmitter ground stations on uplinks to receiving ground stations via downlinks. Thus a satellite of this kind regularly receives a set of incoming signals, corresponding to “uplink” signals, transmitted by the transmitter ground stations and distributed over a set of input channels of the satellite and, in accordance with a predetermined configuration, routes those signals to output channels: a set of outgoing signals is then transmitted by the satellite to the receiving ground stations. In this context one refers to routing signals on board the satellite via the digital processor with which it is equipped. The configuration for routing signals in present-day satellites is most often static. Thus once set up by the satellite it is unchangeable or at the least slowly reconfigurable.
Satellites currently in use sometimes include analog processors. Such processors generate routes linking input channels to output channels that conventionally have a bandwidth in the range 5 to 50 MHz. However, satellites being developed now may include digital processors, notably enabling each satellite to handle a greater number of channels, smaller and more programmable bandwidths, and making it possible to increase connectivity between inputs and outputs.
In the context of the invention, of particular relevance are communication satellites including digital transparent processors. As is known in the art, a digital transparent processor is a digital processor that enables each incoming channel to be divided into sub-channels of variable width, typically in the range from a few hundred kHz to a few MHz. Moreover, the qualifier “transparent” is the opposite of “regenerative”: regenerative processors carry out processing aiming to demodulate the transmitted signals; this is not the object of a digital transparent processor, which does not modify the form of the received signals.
Accordingly, some recent satellites have digital transparent processors enabling routing and control of any input sub-channel to any output sub-channel. This also enables optimization of the gain required for each signal on each sub-channel.
In this context, the main failing of present-day technologies is that the digital transparent processors used are static or quasi-static. In other words, reconfiguring the routing of signals on board present-day satellites, even the most recent ones, is very slow: it is impossible to change it several times per second, whereas the uplink signal to the satellite may, in some cases, change frequency at a rate much higher than once per second. It is therefore impossible for the digital processor to track the instantaneous evolution of the received signal.